The present invention relates to a high-speed optic-electric telecommunication device. More particularly, the present invention provides an integrated photo detector with improved electrostatic discharge damage threshold and a method of making the same.
Over the last few decades, the use of broadband communication networks exploded. In the early days Internet, popular applications were limited to emails, bulletin board, and mostly informational and text-based web page surfing, and the amount of data transferred was usually relatively small. Today, Internet and mobile applications demand a huge amount of bandwidth for transferring photo, video, music, and other multimedia files. For example, a social network like Facebook processes more than 500TB of data daily. With such high demands on data and data transfer, existing data communication systems need to be improved to address these needs.
As science and technology are updated rapidly, processing speed and capacity of the computer increase correspondingly. The communication transmission or reception using the traditional cable is limited to bandwidth and transmission speed of the traditional cable and mass information transmission required in modern life causes the traditional communication replaces the traditional communication transmission system gradually for systems requiring higher bandwidth and longer distance that electrical cable cannot accommodate. With the advances of optical communication technology and applications driven by the market demand on increasing bandwidth and decreasing package footprint, more intensive effort and progress have been seen in the development of silicon photonics on integrating electro-photonic circuits on silicon-on-insulator (SOI) substrate for forming high-speed high-data-rate broadband optic-electric telecommunication devices.
In these broadband optical telecommunication devices based on silicon photonics technology, Ge photodiode is commonly used as a photon detector for monitoring high-speed optical signal transmission since it can be integrated onto silicon or SOI substrate monolithically. However, high-speed Ge photodiode is vulnerable to electrostatic discharge damage (ESD). Because of its low ESD threshold, many silicon photonics communication modules having Ge photo detectors suffered low assembly yield. On the other hand, traditional ESD protection techniques including schemes of using steering-diode arrays, transient-voltage-suppressor (TVS) diodes, and Zener diodes by external chips are mostly geared for electronics module only but not for handling photo detection so as to not suit for being implemented into the silicon photonics devices. FIG. 1 shows examples of conventional ESD protection circuit diagrams with Zener diodes. Each Zener diode (or a Zener diode pair) is used as an external chip for connecting in parallel (either in phase or out of phase) with a subject high-speed Ge photodiode (Ge PD). The Zener diode requires highly doped base region and is not regularly formed in a same process for forming the Ge PD on the SOI substrate for high-speed optic-electric communication applications. Typically, for providing ESD protection purpose, the Zener diode chip is formed separately and mounted or connected to a photodiode chip by solder bump or wire bonding, making the silicon photonics integration level much lower and vulnerable to reliability and assembly yield issue.
Therefore, it is desired to develop improved photodiode devices/circuits with improved ESD threshold for the integrated silicon photonics devices.